Fiber reinforced composite materials are now widely used in a variety of applications where high strength to weight ratios and the ability to be readily molded into complicated shapes are desirable. Polymer composites typically comprise a fibrous or particulate reinforcement distributed in a thermosetting or thermoplastic resin matrix. In such composite materials, an applied load is transferred from the matrix to the reinforcement which is typically a very stiff material. While the reinforcement improves the strength of the matrix, the toughness and crack resistance of the composite is generally not improved and is often less than that of the matrix material alone. This reduction in toughness and crack resistance has been attributed to the high stress concentrations which normally develop at the fiber-matrix interface during loading, and to internal stresses created at the fiber-matrix interface during the curing process because of the difference between the thermal expansion coefficient of the matrix and that of the fibers.
U.S. Pat. No. 4,478,963 to McGarry relates to a composite comprising filler particles having a thin film of a reactive liquid polymer embedded in a polymeric matrix made by mixing the reactive liquid polymer and the filler in order to provide a thin film of the reactive liquid polymer on the filler particles, mixing the coated filler particles with a polymeric matrix, and forming the composite. This patent generally discloses reactive polymer coated filler materials which are embedded in a polymeric matrix to improve fracture toughness and hence does not relate to improving the crack resistance and energy to failure of composites strengthened with fiber reinforcement.